Introduction

Farmers, villagers, and city-dwellers worldwide have recently begun to notice what atmospheric scientists have known for decades: the Earth's climate is changing. During the last five years, extreme and often catastrophic weather events have captured the attention of scientists, public citizens, politicians, and the media. Twice in five years, the “hundred-year” windstorm blew across the United Kingdom, overturning historic structures, uprooting centuries-old trees, and reshaping the countryside. In the same period, the United States, France, and parts of Africa were racked by droughts of historical proportions. Major floods swept across India, Bangladesh, the Sudan, and China, leaving thousands homeless and destitute. Hot spells killed hundreds in Greece. Fierce storms, as harsh as the “Hurricane of the Century,” twice battered the coasts of the United States, thrashed vulnerable islands in the Caribbean, and wreaked havoc on the Pacific Island of Guam.

During earlier times and in most cultures, events like these would have been viewed with cosmic significance. In the history of ancient China, for example, the confluence of natural disasters was interpreted as a divine message. A series of unusual and extreme weather events might signal the imminent end of an aging dynasty. It marked the disintegration of the old order, the emperor's loss of “the mandate of Heaven,” and the opportunity to establish a new regime.

In recent years, abrupt atmospheric changes have similarly captured public attention and influenced human affairs, reshaping the global politics of the environment.